US3063501A

US3063501A - Hydraulic impact tool

Info

Publication number: US3063501A
Application number: US153150A
Authority: US
Inventors: David A Britton
Original assignee: Individual
Current assignee: Individual
Priority date: 1961-11-17
Filing date: 1961-11-17
Publication date: 1962-11-13
Anticipated expiration: 1979-11-13

Description

Nov. 13, 1962 D. A. BRITTON HYDRAULIC IMPACT TOOL 2 Sheets-Sheet 1 Filed NOV. 1'7, 1961 MNA lfjg; 11

Nov. 13, 1962 D. A. BRITTQN HYDRAULIC IMPACT TOOL 2 Sheets-Sheet 2 Filed Nov. 17, 1961 INVENTOR .24 W0 4. de/rra/v ATTORNEY United States Patent ()fiice 3,063,501 Patented Nov. 13, 1952 v j 7 HYDRAULIC HMPACT TOOL David A. Britten, 1104 August Drive, Houston 27, Tex. Filed Nov. 17, 1961, Ser. No. 153,150 9 Claims. (Cl. 166178) This invention relates to well apparatus, and more particularly to a hydraulic impact tool or hydraulic jar designed to impart an impact to well tools are other objects lodged in a well bore for the purpose of removing the same.

As is well known, broken drills, broken sections of pipe, and other objects occasionally become lodged in the bore of a well during drilling operations, and when this occurs, the drilling operations must be suspended until the objects have been removed. This often requires long and tedious fishing operations, and in order to facilitate the removal of such objects it has heretofore been proposed to utilize various types of jarring mechanisms to impart an impact to the object lodged in the well bore in order to free the same, and such jarring mechanisms have also included those of the so-called hydraulic type, in which a fluid is utilized to facilitate building up a force or tension in a pipe string or the like, which when released imparts an upward impact to the objects lodged in the well bore in order to free the same.

Many of the prior art hydraulic jar mechanisms are exceedingly complex, requiring a relatively large number of parts, which not only materially increases the cost of such devices, but also render the same subject to frequent failure, thereby increasing the cost of well drilling operations, but in the case of many of these prior art hydraulic jar mechanisms, the desired result was notebtained, by reason of the fact that such mechanism not only delivered an upward impact to the object lodged in the well, but in resetting the mechanism for delivering a further impact, an impact was also delivered in the downward direction, which often resulted in more firmly lodging the objects in the well bore. In other words, these prior art hydraulic jar mechanisms deliver an impact in both upward and downward directions, whereas the only efiective impact is in an upward direction, and the downward impact is not only unnecessary and wasteful, but is also a distinct disadvantage in that the mechanism may be damaged by the uncontrollable downward blow usually accomplished by blindly lowering the drill string.

A further disadvantage of prior art hydraulic jarring mechanisms is the fact that the piston utilized in such mechanisms has been provided on an inner member or mandrel which is usually hollow or tubular, to permit passage of a wire line or other device therethrough, and in order to obtain a suflicient piston area, it has been necessary to restrict the diameter of the passage in the mandrel or in a member, thereby materially reducing the size of a tool or other device which may be passed downwardly through the hydraulic jarring mechanism. Unfortunately, this deficiency cannot be overcome merely by making the entire hydraulic jarring mechanism of greater diameter, since the outer diameter of such mechanism is limited by the diameter of the well bore in which the same is to be utilized. Consequently, it would be highly desirable to provide a hydraulic impact tool or hydraulic jar which will provide a sufficient upwardly directed force resulting in an impact providing the desired result, which at the same time permits the provision of a relatively large diameter passage through the mandrel or inner member of the tool in order to permit downward passage of relatively large tools for various uses.

It is accordingly an object of the present invention to provide a hydraulic impact tool designed to deliver an impact only in one direction.

A further object of the invention is the provision of a hydraulic impact tool which is relatively simple in construction, embodying only three major relatively movable parts, thereby reducing the cost of manufacture, and providing a long-wearing, dependable device.

A still further object of the invention is the provision of a hydraulic impact tool designed to deliver an impact in one direction only, and which may be rapidly reset for delivering a further impact in the same direction.

Another object of the invention is the provision of a hydraulic impact tool utilizing a closed fluid chamber and a fluid of low viscosity, such as motor oil.

A further object of the invention is the provision of a hydraulic impact tool having a tubular, inner member or mandrel, and in which the diameter of the passage through the inner member or mandrel is relatively large, while the external diameter of the tool is maintained within the required limits.

A still further object of the invention is the provision of a hydraulic impact tool including a closed fluid chamber, there being an inwardly projecting annular shoulder intermediate the length of the chamber, and a slidable sleeve valve provided within the chamber to permit a build-up of pressure in one direction, and the delivering of an impact in one direction, as well as a resetting operation devoid of any substantial pressure build-up.

A further object of the invention is the provision of a hydraulic impact tool, including a closed fluid chamber between two pistons connected by a mandrel, there being an inwardly extending annular shoulder in the chamber, such shoulder providing an area sulficient to permit a build-up of high pressure, thereby permitting the use of pistons and mandrel of maximum diameter to provide a relatively large passage thereth-rough, while maintaining the outer diameter of the tool within necessary limits.

A still further object of the invention is the provision of a hydraulic impact tool including a hollow body having two pistons therein connected by a mandrel to provide a closed fluid chamber between the pistons, and an annular shoulder on the body projecting into the chamber, the volume of the chamber remaining constant, regardless of the axial position of the pistons with respect to the body.

Another object of the invention is the provision of a hydraulic imp-act tool having slidable and non-rotatably interrelated parts which permits applying a torque in either direction through the impact tool to a fishing tool or other device to which the impact tool is attached,

Further objects and advantages of the invention will be apparent from the following description taken in conjunction with the accompanying drawings, wherein:

FIG. la is a longitudinal sectional view showing the upper portion of a hydraulic impact tool constructed in accordance with this invention;

FIG. 1b, a longitudinal sectional view showing the lower end of the hydraulic impact tool of this invention;

FIG. 2, a longitudinal sectional view to an enlarged scale showing the fluid chamber portion of the device, as well as the relationship between the inwardly projecting shoulder and the slidable valve sleeve which surrounds the mandrel within the fluid chamber;

FIG. 3, a side elevational view of the valve sleeve which slidably surrounds the mandrel in the fluid chamber;

FIG. 4, a sectional view taken substantially on the line 44 of FIG. 1a, and showing the relationship of the mandrel, the slidable valve sleeve, the inwardly projecting shoulder, and the outer body of the tool; and,

FIG. 5, a sectional View taken substantially on the line 5--5 of FIG. lb, and showing the means utilized for providing a slidable and non-rotatable connection between the mandrel and the body of the tool.

With continued reference to the drawings, there is shown a hydraulic impact tool constructed in accordance with this invention, and which may well comprise an upper elongated hollow body portion 10, there being a coupling member 11 removably secured by screw threaded or other suitable means 12 to the upper end of the upper body portion 10, the coupling member 11 being provided with screw-threaded means 13 for removably securing the same to the lower end of a drill string. Suitable packing means 14 may be provided between the coupling member 11 and the upper body portion It to prevent leakage of fluid at this point.

A lower elongated hollow body portion 19 is removably secured by screw-threaded or other suitable fastening means 20 to the lower end of the hollow body portion 10, and suitable packing means 21 may be provided to prevent leakage of fluid at this point.

An elongated hollow mandrel 22 is slidably disposed in the upper body portion 10, and the mandrel 22 is provided with a piston 23 at the upper end thereof. It is to be noted that the piston 23 on the mandrel 22 slidably engages the inner surface 24 of the upper body portion 10, and at the lower end of the piston 23 there is provided suitable packing means 25 secured in place by a snap ring or other suitable means 26, with the packing means 25 slidably engaging the inner surface 24 of the upper body portion 10 in fluid-tight relationship. If desired, a further suitable packing means 27 may be provided adjacent the upper end of the piston 23. A relatively large passage 28 extends through the mandrel 22.

A valve sleeve 29 of less length than the mandrel 22 slidably surrounds the mandrel 22, and as clearly shown in FIGS. 10:, 2 and 3, the valve sleeve 29 is provided at the upper end with a tapered portion 30, which merges into a cylindrical portion 31, there being an outwardly projecting annular flange 32 at the lower end of the valve sleeve 29, and a reduced portion 33 between the flange 32 and the cylindrical portion 31. A flange 32 may be provided with a plurality of radial slots 32. The purpose and operation of the valve sleeve 29, as Well as the radial slots 32' will be later described. At the lower end of the upper body portion 10 there is provided an inwardly projecting annular shoulder 34, and from an inspection of FIGS. la and 2, it will be seen that the inner diameter of the shoulder 34 is less than the outer diameter of the flange 32, but slightly greater than the outer diameter of the cylindrical portion 31 on the valve sleeve 29, in order to provide a restricted passage 35 between the valve sleeve 29 and the inner surface of the shoulder 34. The purpose of the restricted passage will be later described.

A hollow piston 36 is removably secured to the lower end of the mandrel 22 by screw-threaded or other suitable fastening means 37, and suitable packing means 38 may be provided at this point to prevent leakage of fluid into the passage 28 of the mandrel 22, or the passage 39 of the piston 36, which is in alignment with the passage 28 in the mandrel 22. The upper end of piston 36 provides an abutment 41 for engaging the flange 32 of the valve sleeve 29 to limit downward movement of such valve sleeve on the mandrel 22. Piston 36 and piston 23 are .held in fixed, spaced relationship by mandrel 22, and

serve to provide a closed fluid chamber 43 between the

pistons

23 and 36. The chamber 43 is tilled with oil or other suitable fluid.

A hollow mandrel 44 is slidably received in the lower body portion 19, and is coupled to the lower part of piston 36 in any suitable manner, and the lower end of piston 36 forms an anvil surface 46 for receiving the impact of a hammer in a manner to be later described. Vent openings 48 are provided in the lower body member 19 below the piston 36, in order to permit free flow of fluid into or out of the space within the lower body member 19, in order to prevent an undue pressure build-up during upward and downward movement of the piston 36 in the course of operation of the tool.-

As best shown in FIGS. 1]) and 5, the mandrel 44 is provided with a plurality of elongated, outwardly opening grooves 49, and the lower body portion 19 is provided with a plurality of inwardly opening grooves 50 opposing the grooves 49 in the mandrel '44. Rods 51 are disposed in the grooves 49 and 5t and such rods are maintained against upward movement by engagement with an inwardly projecting shoulder 52 on the lower body portion 19, and are retained in place and against downward movement by a nut 53 secured by screw-threaded means 54 or other suitable means, to the lower end of the lower body portion 19. It will thus be seen that the rods 51 disposed in the grooves 49 and 5t} permit vertical sliding movement of the mandrel 44 with respect to the lower body portion 19, but provide a non-rotatable connection therebetween by means of which torque may be transmitted from the lower body portion 19 to the mandrel 44. The mandrel 44 is provided with a passage 55 therethrough in alignment with the

passages

39 and 28 in the piston 36 and mandrel 22, and the lower end of the integrally formed mandrel 44 is provided with screw-threaded or other suitable means 56 for removably coupling the same to a fishing tool, stuck object, or other device with which the hydraulic impact tool of this invention is to be utilized. The upper surface 57 of the shoulder 52 provides a hammer surface for engaging the anvil surface 46 on the piston 36 in a manner to be presently described.

It is also to be noted that the coupling means 11 at the upper end of the body portion 10 is provided with an axial passage 57 in alignment with the passage 28 in the mandrel 22, and consequently, a wire line, together with any desired tool attached thereto, may be passed downwardly through the entire hydraulic impact tool of this invention, and this operation is materially facilitated by the relatively large diameter of the passage through the impact tool, which is made possible by the particular structure of the impact tool of this invention. This structure provides for a suflicient build-up of pressure in a manner to be presently described, and at the same time permits the inner member or mandrel 22 to be of relatively large diameter, thereby permitting a passage therethrough of relatively large diameter.

With particular reference to FIGS. la and 2, the impact tool of this invention is operated to provide an upward impact by exerting an upward force on the upper body member 10, which results in moving the shoulder 34 upward-1y with respect to the

pistons

23 and 36 on the mandrel 22, which results in compressing fluid within the chamber 43 between the upper surface of the shoulder 34 and the piston 23 on the mandrel 22. As the shoulder 34 moves upwardly by the cylindrical portion 31 on the valve sleeve 29, the restricted annular passage 35 permits a relatively slow bleeding of fluid downwardly to permit continued upward movement of the outer body member 10 with respect to the

pistons

23 and 36, and upon reaching a position above the cylindrical portion 31 on the valve sleeve 29, fluid will flow rapidly from the portion of the chamber 43 above the shoulder 34, to the portion below such shoulder, thereby resulting in a rapid upward movement of the outer body portion 10, and an impact between the hammer surface 57 and the anvil surface 46.

In order to reset the impact tool of this invention for a further operation, the upper body portion 10 is allowed to move downwardly, with the result that the slight pressure created in the lower portion of chamber 43 by downward movement of the shoulder 34 will result in moving the valve sleeve 29 upwardly to the position shown in FIG. la, at which point fluid will flow readily from the lower portion of the chamber 43 through the slots 32, and by the reduced portion 33 to the upper portion of the chamber 43, and the upper body portion it) may continue to move downwardly with the shoulder 34 contacting the flange 32 on the valve sleeve 29 to move the same downwardly to the position shown in FIG. 2, thereby resetting the tool for further operation.

It should be noted that during the above-described operation of the tool that the volume of chamber 43 between

pistons

23 and 36 remains constant, regardless of the axial position of

pistons

23 and 36, with respect to shoulder 34, or the upper and

lower body portions

19 and 19.

Obviously, the impact tool of this invention may be constructed to operate in an inverted position with respect to that described above, in which case the threaded end 56 of mandrel 44 would be coupled to the drill string, and the coupling member 11 connected to a grappling tool or other suitable device.

It will be seen that by the above-described invention, there has been provided a relatively simple, yet highly eflective hydraulic impact tool which may be utilized to provide an impact only in one direction, and which by reason of the novel structure thereof, permits a passage through the tool of relatively large diameter in order to permit the passage of a wire line and other tools therethrough.

It will be obvious to those skilled in the art that various changes may be made in the invention, without departing from the spirit and scope thereof, and therefore the invention is not limited by that which is shown in the drawings, and described in the specification, but only as indicated in the appended claims.

What is claimed is:

l. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to a drill string, a lower elongated hollow body portion removably secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston at the upper end, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having a tapered upper end merging into an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a reduced portion between said flange and said cylindrical portion, radial slots in said flange, an inwardly projecting annular shoulder adjacent the lower end of said upper body portion, the inner diameter of said shoulder being less than the outer diameter of said flange but slightly greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel and providing an abutment to limit downward movement of said sleeve, said pistons roviding a fluid-receiving chamber therebetween, a second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, elongated grooves in said second mandrel, grooves in said lower body portion opposing the grooves in said second mandrel, rods disposed in said grooves in said lower body portion and engaging the grooves in said second mandrel to provide a slidable non-rotatable connection, a nut on the lower end of said lower body portion removably securing said rods in place, and means on the lower end of said second man- ,drel for removably coupling the same to a fish or stuck object.

2. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to a drill string, a lower elongated hollow body portion removably secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston at the upper end, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon,

tion, the inner diameter of said shoulder being less than.

the outer diameter of said flange but slightly greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel and providing an abutment to limit downward movement of said sleeve, said piston providing a fluid-receiving chamber therebetween, a second hollow mandrel slidably received in said body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, elongated grooves in said second mandrel, grooves in said lower body portion opposing the grooves in said second mandrel, rods disposed in the grooves in said lower body portion and engaging the grooves in said second mandrel to provide a slidable nonrotatable connection, and means on the lower end of said second mandrel for removably coupling the same to a fish or stuck object.

3. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said body portion for coupling the same to a drill string, a lower elongated hollow body portion removably secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston at the upper end, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having a tapered upper end merging into an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a reduced portion between said flange and said cylindrical portion, radial slots in said flange, an inwardly projecting annular shoulder adjacent the lower end of said upper body portion, the inner diameter of said shoulder being less than the outer diameter of said flange, but slightly greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel and providing an abutment to limit downward movement of said sleeve, said pistons providing a fluid-receiving chamber therebetween, a second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, means providing a slidable and non-rotatable connection between said lower body portion and said second mandrel and means on the lower end of said second mandrel for removably coupling the same to a fish or stuck object.

4. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to a drill string, a lower elongated hollow body portion removably secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston at the upper end, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having a tapered upper end merging into an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a reduced portion between said flange and said cylindrical portion, slots in said flange, an inwardly projecting annular shoulder adjacent the lower end of said upper body portion, the inner diameter of said shoulder being less than the outer diameter of said flange but slightly greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel and providing an abutment to limit downward movement of said sleeve, said pistons providing a fluid-receiving chamber therebetween, a second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil sur face, an internal shoulder on said lower body providing a hammer, means providing a slidable and non-rotatable connection between said lower body portion and said second mandrel and means on the lower end of said second mandrel for removably coupling the same to a fish or stuck object.

5. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to a drill string, a lower elongated hollow body portion removably secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston at the upper end, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a reduced portion between said flange and said cylindrical portion, slots in said flange, an inwardly projecting annular shoulder adjacent the lower end of said upper body portion, the inner diameter of said shoulder being less than the outer diameter of said flange but slightly greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel and providing an abutment to limit downward movement of said sleeve, said pistons providing a fluid-receiving chamber therebetween, a second hollow mandrel slidably received in said lower body portion and connected to said piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, means providing a slidable and non-rotatable connection between said lower body portion and said second mandrel, and'means on the lower end of said second mandrel for removably coupling the same to a fish or stuck object.

6. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to a drill string, a lower elongated hollow body portion removably secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston thereon, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve, and a reduced portion between said flange and said cylindrical portion, slots in said flange, an inwardly projecting annular shoulder in said upper body portion, the inner diameter of said shoulder being less than the outer diameter of said flange but slightly greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel, said pistons providing a fluid-receiving chamber therbetween, a second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, mean providing a slidable and non-rotatable connection between said lower body portion and said second mandrel and means on the lower end of said second mandrel for removably coupling the same to a fish or stuck object.

7. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to a drill string, a lower elongated hollow body portion secured to the lower end of said upper body portion, an elongated, hollow mandrel slidablydisposed in said upper body portion, said mandrel having a piston thereon, packing means on said piston slidably engagingsaid upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slid-ably received thereon, said sleeve having an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a re-- duced portion between said flange and said cylindrical portion, slots in said flange, an inwardly projecting annular shoulder in aid upper body portion, the inner diameter of said shoulder being greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel, said pistons providing a fluid-receiving chamber therebetween, a second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, means for providing a slidable and non-rotatable connection between said lower body portion and said second mandrel, and means on the lower end of said second mandrel for removably coupling the same to a fish or stuck object.

8. A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to another hollow member, a lower elongated hollow body portion secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston thereon, packing means on said piston slidably engaging said upper body portion in fluid-tight relationship, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a reduced portion between said flange and said cylindrical portion, slots in said flange, an inwardly projecting annular shoulder in said upper body portion, the inner diameter of said shoulder being greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel, said pistons providing a fluid-receiving chamber therebetween, the volume of said chamber remaining constant regardless of the axial position of said pistons with respect to said shoulder and said upper and lower body portions, 2 second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, means providing a slidable and non-rotatable connection between said lower body portion and said second mandrel, and means on the lower end of said second mandrel for removably coupling the same to a member operatively associated therewith.

9, A hydraulic impact tool comprising an upper elongated hollow body portion, means on the upper end of said upper body portion for coupling the same to another hollow member, a lower elongated hollow body portion secured to the lower end of said upper body portion, an elongated hollow mandrel slidably disposed in said upper body portion, said mandrel having a piston thereon, a valve sleeve of less length than said mandrel slidably received thereon, said sleeve having an enlarged cylindrical portion, an outwardly projecting flange at the lower end of said sleeve and a reduced portion between said flange and said cylindrical portion, slots in said flange, an inwardly projecting annular shoulder in said upper body portion, the inner diameter of said shoulder being greater than the outer diameter of said cylindrical portion, a hollow piston secured to the lower end of said mandrel, said pistons providing a fluid-receiving chamber therebetween, the volume of said chamber remaining constant regardless of the axial position of said pistons with respect to said shoulder and said upper and lower body portions, a second hollow mandrel slidably received in said lower body portion and connected to said hollow piston, the lower end of said hollow piston providing an anvil surface, an internal shoulder on said lower body portion providing a hammer, means providing a slidable and nonl0 rotatable connection between said lower body portion and said second mandrel, and means on the lower end of said second mandrel for removably coupling the same to a member operatively associated therewith.

No references cited.

UNITED STATES PATENT OFFICE CERTIFICATE F CCRRECTION Patent No, 3,063,501 November 13 1962 David A, Britten I It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below In the heading tothe printed specification, line 3, for "1104 August Drive" read 110d Augusta Drive column 1, line 9, for "are read or Signed and sealed this 21st day of May 1963,.

SEAL) ttest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents